的Android捕捉视频错误

Question

我需要从相机捕获视频并保存到存储卡中，我使用google tutorial，我仍然会得到一个错误调用

mRecorder.setCamera(mCamera); // 4.b.1 step from tutorial 

时候我已经尽量把它放在try和看到异常

try { 
    mRecorder.setCamera(mCamera); 
} catch(Exception e) { 
    Log.d("MyVideoRecord", "Error setting the camera: " + e.getMessage()); 
    System.out.println("CameraPreview::record() - setCamera() thrown an exception"); 
    System.out.println("Exception: "+e.getMessage()); 
    System.out.println("Exception: "+e.getLocalizedMessage()); 
    System.out.println("Exception: "+e.toString()); 
    e.printStackTrace(); 

    return false; 
} 

logcat的输出

D/MyVideoRecord(2681): Error setting the camera: null 
I/System.out(2681): CameraPreview::record() - setCamera() thrown an exception 
I/System.out(2681): Exception: null 
I/System.out(2681): Exception: null 
I/System.out(2681): Exception: java.lang.NullPointerException 
W/System.err(2681): java.lang.NullPointerException 
W/System.err(2681):  at com.example.myvideorecord.CameraPreview.record(CameraPreview.java:101) 
W/System.err(2681):  at com.example.myvideorecord.MainActivity.onOptionsItemSelected(MainActivity.java:104) 
W/System.err(2681):  at android.app.Activity.onMenuItemSelected(Activity.java:2502) 
W/System.err(2681):  at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:969) 
W/System.err(2681):  at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735) 
W/System.err(2681):  at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149) 
W/System.err(2681):  at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874) 
W/System.err(2681):  at com.android.internal.view.menu.IconMenuView.invokeItem(IconMenuView.java:468) 
W/System.err(2681):  at com.android.internal.view.menu.IconMenuItemView.performClick(IconMenuItemView.java:126) 
W/System.err(2681):  at android.view.View$PerformClick.run(View.java:14263) 
W/System.err(2681):  at android.os.Handler.handleCallback(Handler.java:605) 
W/System.err(2681):  at android.os.Handler.dispatchMessage(Handler.java:92) 
W/System.err(2681):  at android.os.Looper.loop(Looper.java:137) 
W/System.err(2681):  at android.app.ActivityThread.main(ActivityThread.java:4441) 
W/System.err(2681):  at java.lang.reflect.Method.invokeNative(Native Method) 
W/System.err(2681):  at java.lang.reflect.Method.invoke(Method.java:511) 
W/System.err(2681):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
W/System.err(2681):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
W/System.err(2681):  at dalvik.system.NativeStart.main(Native Method) 
D/dalvikvm(2681): Debugger has detached; object registry had 425 entries 

它看起来像mCamera指针从日志中为空，但我不认为这就是这种情况，因为我已经解锁mCamera没有错误。 我看了documentation，但没有任何关于setCamera()的信息返回错误或抛出异常。我在清单中设置了CAMERA,WRITE_EXTERNAL_STORAGE和RECORD_AUDIO权限。我不知道可能是什么原因导致问题或如何追踪它。任何人都可以帮我吗？

非常感谢！ :)

---

这里是我的所有代码：

CameraPreview.java

我已经实现record()（这是wher发生错误时）和stopRecord()方法。其余的文件是从谷歌教程。

package com.example.myvideorecord; 

import java.io.File; 
import java.io.IOException; 

import android.content.Context; 
import android.hardware.Camera; 
import android.media.CamcorderProfile; 
import android.media.MediaRecorder; 
import android.net.Uri; 
import android.os.Environment; 
import android.util.Log; 
import android.view.SurfaceHolder; 
import android.view.SurfaceView; 

//http://developer.android.com/guide/topics/media/camera.html#capture-video 
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { 
     private SurfaceHolder mHolder; 
     private Camera mCamera; 
     private boolean recording; 
     private MediaRecorder mRecorder; 

     public CameraPreview(Context context, Camera camera) { 
      super(context); 
      System.out.println("CameraPreview() - Started"); 
      mCamera = camera; 
      recording = false; 

      // Install a SurfaceHolder.Callback so we get notified when the 
      // underlying surface is created and destroyed. 
      mHolder = getHolder(); 
      mHolder.addCallback(this); 
      // deprecated setting, but required on Android versions prior to 3.0 
      mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); 

      System.out.println("CameraPreview() - Ended"); 
     } 

     public void surfaceCreated(SurfaceHolder holder) { 
      System.out.println("CameraPreview::surfaceCreated() - Started"); 
      // The Surface has been created, now tell the camera where to draw the preview. 
      try { 
       mCamera.setPreviewDisplay(holder); 
       mCamera.startPreview(); 
      } catch (IOException e) { 
       Log.d("MyVideoRecord", "Error setting camera preview: " + e.getMessage()); 
      } 

      System.out.println("CameraPreview::surfaceCreated() - Ended"); 
     } 

     public void surfaceDestroyed(SurfaceHolder holder) { 
      System.out.println("CameraPreview::surfaceDestroyed()"); 
      // empty. Take care of releasing the Camera preview in your activity. 
     } 

     public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { 
      System.out.println("CameraPreview::surfaceChanged() - Started"); 

      // If your preview can change or rotate, take care of those events here. 
      // Make sure to stop the preview before resizing or reformatting it. 

      if (mHolder.getSurface() == null){ 
       // preview surface does not exist 
       return; 
      } 

      // stop preview before making changes 
      try { 
       mCamera.stopPreview(); 
      } catch (Exception e){ 
       // ignore: tried to stop a non-existent preview 
      } 

      // set preview size and make any resize, rotate or 
      // reformatting changes here 

      // start preview with new settings 
      try { 
       mCamera.setPreviewDisplay(mHolder); 
       mCamera.startPreview(); 

      } catch (Exception e){ 
       Log.d("MyVideoRecord", "Error starting camera preview: " + e.getMessage()); 
      } 

      System.out.println("CameraPreview::surfaceChanged() - Ended"); 
     } 


     public boolean record() 
     { 
      // if already recording, return 
      if(recording) return false; 

      // We are recording 
      recording = true; 
      // log start of the method 
      System.out.println("CameraPreview::record() - Method start"); 

      //mCamera.stopPreview(); 
      mCamera.unlock(); 


      // 
      // !!! THIS IS WHERE ERROR OCCURS !!! 
      // 
      // 
      try { 
       mRecorder.setCamera(mCamera); 
      } catch(Exception e) { 
       Log.d("MyVideoRecord", "Error setting the camera: " + e.getMessage()); 
       System.out.println("CameraPreview::record() - setCamera() thrown an exception"); 
       System.out.println("Exception: "+e.getMessage()); 
       System.out.println("Exception: "+e.getLocalizedMessage()); 
       System.out.println("Exception: "+e.toString()); 
       e.printStackTrace(); 

       return false; 
      } 

      // Set media recorder properties    
      mRecorder.setAudioSamplingRate(MediaRecorder.AudioSource.CAMCORDER); 
      mRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA); 
      mRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_LOW)); 
      //mRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString()); 
      mRecorder.setOutputFile("/sdcard/MVR_video"); 

      // probably not needed 
      //mRecorder.setPreviewDisplay()); 

      // Prepare media recorder 
      try { 
       mRecorder.prepare(); 
      } catch (Exception e) { 
       Log.d("MyVideoRecord", "Error preparing media recorder: " + e.getMessage()); 
       System.out.println("CameraPreview::record() - prepare() thrown an exception"); 

       return false; 
      } 

      mRecorder.start(); 

      System.out.println("CameraPreview::record() - Method returning TRUE"); 
      return true; 
     } 

     public void stopRecord() { 
      System.out.println("CameraPreview::stopRecord() - Method start"); 

      if(recording) 
      { 
       mRecorder.stop(); 
       mRecorder.release(); 
       mCamera.lock(); 
      } 
     }  
    } 

MainActivity.java

package com.example.myvideorecord; 

import android.app.Activity; 
import android.content.SharedPreferences; 
import android.hardware.Camera; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.widget.FrameLayout; 

// http://developer.android.com/reference/android/app/Activity.html 
public class MainActivity extends Activity { 
    private Camera mCamera; 
    private CameraPreview mPreview; 
    private Camera.Parameters parameters; 
    private FrameLayout preview; 
    private SharedPreferences preferences; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.camera_preview);    

     // Create an instance of Camera 
     mCamera = getCameraInstance(); 

     // Get parameters of camera (not neccessary now) 
     parameters = getCameraParameters(mCamera); 
     parameters.getFocusMode(); 

     // get preview reference 
     preview = (FrameLayout) findViewById(R.id.camera_preview); 

     mPreview = new CameraPreview(this, mCamera); 

     preferences = getPreferences(MODE_PRIVATE); 
    } 

    @Override 
    public void onStart() { 
     super.onStart(); 

     // Create our Preview view and set it as the content of our activity.   

     System.out.println("MainActivity::onCreate() - adding view to preview"); 
     preview.addView(mPreview); 
     System.out.println("MainActivity::onCreate() - view added"); 
    } 
    @Override 
    public void onStop() { 
     super.onStop();  
     System.out.println("MainActivity::onStop() - Method start"); 

     // here shoud go something like 
     // preview.stop 
     preview.removeView(mPreview); 
     mPreview.stopRecord(); 
    } 

    @Override 
    public void onPause() { 
     super.onPause(); 

     // Save all needed information 
     //preferences.edit(); 
    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     System.out.println("MainActivity::onDestroy() - Method start"); 

     mCamera.stopPreview(); 
     releaseCameraInstance(mCamera); 
    } 



    /* 
    * 
    * MENU 
    * 
    * */ 
    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     System.out.println("MainActivity::onCreateOptionsMenu() - Method start"); 

     getMenuInflater().inflate(R.menu.activity_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     System.out.println("MainActivity::onOptionsItemSelected() - Method start"); 

     // Handle item selection 
     switch (item.getItemId()) { 
      case R.id.menu_settings: 
       return true; 
      case R.id.menu_quit: 
       this.finish(); 
       return true; 
      case R.id.menu_record: 
       mPreview.record(); 
       return true; 
      default: 
       return super.onOptionsItemSelected(item); 
     } 
    } 



    /* 
    * 
    * Camera handling 
    * 
    * */ 
    /** A safe way to get an instance of the Camera object. */ 
    public static Camera getCameraInstance(){ 
     Camera c = null; 
     try { 
      c = Camera.open(); // attempt to get a Camera instance 
     } 
     catch (Exception e){ 
      // Camera is not available (in use or does not exist) 
      System.out.println("getCameraInstance() - excepction"); 
     } 

     System.out.println("getCameraInstance() - returning camera"); 
     return c; // returns null if camera is unavailable 
    } 

    public static Camera.Parameters getCameraParameters(Camera c) 
    { 
     System.out.println("getCameraParameters() - getting parameters of camera"); 
     Camera.Parameters par; 
     par = c.getParameters(); 

     System.out.println("getCameraParameters() - returning parameters of camera"); 
     return par; 
    } 

    /* release camera object and log it */ 
    public static void releaseCameraInstance(Camera c){ 
     System.out.println("releaseCameraInstance() - camera released"); 
     c.release(); 
    } 
} 

Answer 1

你mRecorder为空，你永远不会初始化。与相机和其他东西一起构造函数初始化这一点;）

mRecorder = new MediaRecorder();